Joint Subchannel Pairing and Power Allocation in Multichannel MAB CBased Two-Way Relaying
Abstract: We consider amplify-and-forward two-way relaying in a multichannel system with two end nodes and a single relay, with a two-slot multiaccess broadcast (MABC) relaying strategy. We investigate the problem of joint subchannel pairing and power allocation to maximize the achievable sum-rate in the network under the individual power constraints. We propose an iterative approach to solve this challenging mixed-integer programming problem by decomposing it into subchannel pairing optimization and joint power allocation optimization, and solving them iteratively. For subchannel pairing at the relay, we show that, unlike in the one-way relaying case, there exists no explicit SNR-based low-complexity subchannel pairing strategy that is optimal for two-way relaying, and the optimal pairing needs to be performed numerically. Nonetheless, we propose an effective low-complexity suboptimal pairing scheme based on an effective SNR metric. For joint power allocation at all nodes, the optimization problem is nonconvex. We propose an iterative procedure to optimize the power at the two end nodes and at the relay iteratively. Using a problem transformation, we show that each power optimization subproblem turns out to be convex and can be solved efficiently. Our proposed iterative procedure is guaranteed to converge to a locally optimal solution. We then generalize our approach to the weighted sum-rate maximization problem. Simulation results demonstrate the effectiveness of the
proposed pairing scheme, as well as the gain of joint optimization approach over other pairing-only or power-allocation-only optimization approaches.